Reference values of pulmonary diffusing capacity during exercise by a rebreathing technique

C. C W Hsia, D. G. McBrayer, M. Ramanathan

Research output: Contribution to journalArticlepeer-review

87 Scopus citations


Normal reference values of the pulmonary diffusing capacity for carbon monoxide (DL(CO)), diffusing capacity of the membrane (DM(CO)), and pulmonary capillary blood volume (VC) were derived by a rebreathing technique in 44 normal, healthy, nonsmoking individuals ranging from 17 to 68 yr of age. Simultaneous measurements of DL(CO), lung volumes, pulmonary blood flow, and septal tissue volume were determined at rest and during steady-state exercise of 25, 50, and 80% of maximal workload and at two levels of alveolar O2 tension. DM(CO) and VC were calculated using the Roughton-Forster relationship. Using stepwise regression analysis, DL(CO) and DM(CO) (in ml CO/min/mm Hg) were found to be significantly related to pulmonary blood flow (Q̇C in L/min), age (in years), and body surface area (BSA in square meters). VC (in ml) was found to be significantly related to Q̇C and BSA. Normalization of measured date with respect to these variables largely eliminated male versus female differences. We conclude that Q̇C is the most important determinant of the recruitment of diffusing capacity. From rest to near-maximal exercise, DL(CO), DM(CO), and VC increase linearly with respect to Q̇C without evidence of reaching a plateau.

Original languageEnglish (US)
Pages (from-to)658-665
Number of pages8
JournalAmerican journal of respiratory and critical care medicine
Issue number2
StatePublished - Aug 1995

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine


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